The invention relates to a quick-release coupling comprising a male part and a female part, where the female part is composed of a valve stem attached to an inner tubular body so as to define a number of flow channels and an outer body that houses sliders and means of locking and releasing the male part.
it is known that special quick-release connectors or couplings are used to enable a flexible hose to be connected and disconnected swiftly to and from a hydraulic system. Certain quick-release couplings in particular have no projections on their mutually opposing surfaces and are termed flat-faced quick-release couplings. These couplings prevent the ingress of air or the leakage of fluid during connection and disconnection.
Flat-faced quick-release couplings currently consist of a male part and a female part. The male part comprises an outer body and a valve body of standardized geometry and dimensions.
The female part comprises a valve stem fixed by a valve guide to an inner body. The inner body is fixed in turn to an outer body. The valve guide supports the valve stem in the centre of the coupling and defines flow channels for the fluid. An inner slider and an outer slider move internally inside the outer body under the action of springs. The movement of the sliders opens and closes the fluid flow channels. A ring of balls is present in special seats formed in the outer body close to the end that couples onto the male part. A sliding collar subject to spring action is provided around the outside of the body and encloses the ring of balls. The collar locks or releases the ring of balls when pushed into a recess in the male part when the coupling is connected up.
The two parts of the coupling are connected together by pushing the male part against the valve stem and sliders of the female part.
While being pressed against the valve stem of the female part, the valve of the male part retreats inside the male part, thereby opening the fluid flow channels.
These flat-faced quick-release couplings are used as connectors in hydraulic circuits, e.g. in hydraulic circuits for agricultural machinery or earth levelling machines. They are used especially for connecting the hydraulic circuit of a tool to the power unit.
The hydraulic circuit of the tool usually ends at the male part of the coupling.
It often happens that the hydraulic circuit is disconnected, by opening the coupling, while still partially under pressure. In such cases, the male part contains fluid under pressure which makes subsequent reconnection of the coupling very difficult, as the amount of force required for this operation is equivalent to the cross-sectional area of the valve of the male part (cross-sectional area of the coupling equal to the external dimension of a seal of the valve), whose dimensions are sometimes very great, multiplied by the pressure of the internal fluid.
It may also happen that after the hydraulic circuit of a tool has been disconnected from a power unit at a given atmospheric temperature, the fluid remaining inside the tool's hydraulic circuit increases in pressure with a rise in the temperature of the atmosphere.
Tools do not usually include means of adjusting the pressure of the hydraulic circuit and so it is extremely difficult to reconnect the hydraulic circuit of the tool to the power unit. The reason for this is the extreme difficulty of driving back the valve present inside the male part when it is under pressure from the heated fluid contained inside it.